Solid ink jet printers were first offered commercially in the mid-1980""s. One of the first such printers was offered by Howtek Inc. which used pellets of colored cyan, yellow, magenta and black ink that were fed into shape coded openings. These openings fed generally vertically into the heater assembly of the printer where they were melted into a liquid state for jetting onto the receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the printer. These pellets were elongated and tapered on their ends with separate rounded, five, six, and seven sided shapes each corresponding to a particular color.
Later solid ink printers, such as the Tektronix Phaser(trademark), the Tektronix Phaser(trademark) 300, and the Jolt printer offered by Dataproducts Corporation, used differently shaped solid ink sticks that were either gravity fed or spring loaded into a feed channel and pressed against a heater plate to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. One system used an ink stick loading system that initially fed the ink sticks into a preload chamber and then loaded the sticks into a load chamber by the action of a transfer lever. Earlier solid or hot melt ink systems used a flexible web of hot melt ink that is incrementally unwound and advanced to a heater location or vibratory delivery of particulate hot melt ink to the melt chamber.
Basic configurations of a four-color ink loader having independent melt plates have been described in previously issued patents such as, for example, U.S. Pat. Nos. 5,734,402, 5,861,903, and 6,056,394. The disclosures of these patents are hereby incorporated by reference in their entirety.
Embodiments include an ink supply level sensing system for a solid ink loader having a channel for holding ink sticks, the channel having a push block therein, wherein the push block pushes ink sticks towards an end of the channel, and wherein the push block moves down the channel as it pushes the ink sticks. The sensing system includes a vane, an arm connected to the vane, the arm extending into the channel such that it is moved by the push block, thereby moving the vane, a first optical sensor having a first optical transmitter and a first optical receiver, wherein the first optical sensor provides a signal indicating a low ink supply when the vane passes between the first optical transmitter and first optical receiver; and a second optical sensor having a second optical transmitter and a second optical receiver, wherein the second optical sensor provides a signal indicating no ink supply when the vane passes between the second optical transmitter and second optical receiver.